1. Field of the Invention
The invention relates to a stop which settles in a device bore as well as to the device provided with at least one such stop adapted for use particularly in, but not exclusively in, a safety valve.
2 . Description of the Prior Art
Safety valves comprise a body consisting of a chamber into which lead three channels. A first channel accommodates a spring which constantly stresses a valve toward a seat positioned in a duct or passage interposed between the chamber and a second channel which is connected to the source of fluid whose pressure is to be limited.
The valve consists of a dish or diaphragm by means of which said valve is pressed against its seat. The valve accommodates a seal on its face opposite to that which supports the diaphragm and, the valve receives, directly or by means of at least one part, such as a washer or a centering cup, the pressure of the spring which must rest beneath a stop connected to the body so as to enable its spacing relative to its seat to be adjusted and, thereby to adjust the pressure of the calibration of the spring.
As long as the pressure of this fluid remains below that at which the spring has been set, the valve remains pressed against the seat to shut off the passage interconnecting the channels. As soon as this pressure reaches at least the pressure at which the spring has been set, the valve rises from its seat and the fluid invades the chamber from where it escapes by means of the third channel, which is usually connected to a discharge circuit or conduct.
The support stop of the spring is also freely traversed in axial direction by a manual-lift rod whose head is gripped by an operating key.
Heretofore, for the connection to the body of the stop under which the spring is pressed directly or indirectly, this stop is usually screwed into the bore of the body or onto the external surface of the channel. This mode of installation, which requires elaborate machining operations and a relatively long setup time, results in a relatively high cost of production.
To eliminate this disadvantage, it is common practice to use stops made of steel plate hollowed out in such a way as to form a spring-centering dish to the edge of which is connected by a slight round-off a skirt which rises concentrically to the dish until about half-way before flaring into a relatively large truncated collar.
When this stop is fitted tight in its bore, taking account of the conical shape of the collar, the skirt tends to pull back elastically, whereas, when the spring pushes on the bottom of the dish, the edge of the collar is pressed in the wall of the bore, resulting in self-locking.
Unfortunately, since it presses only with its collar against the bore wall, this hollowed-out steel plate stop is not very stable.
To overcome this drawback, it is common practice to wedge in the dish a guide which cooperates, for example, with the manual-lift rod. However, this construction results in a cost price which is at least as high as for a screwed assembly.